Answer:
u need to go on a long distance and then ask the judge for the judgment....
and it will be tested as the judge will call the doctor...
enjoy
http://www.patentstorm.us/patents/640448...
that might not be what your looking for.. but i thought it MIGHT help sorry if it dosnt.
Also relate it to things that you know, for example you know how big a football field is just imagine so many of those for your distance or say you know exacly how long a shcool bus is try imagining so many school buses to that distance
by measuring.
if you are talking about bigger distances you can do so by using tall landmarks. if you know how tall a landmark is you can measure how many degrees a line from you to the top of the landmark is. once you have done that you can calculate the distance to the object.
another option for even larger distances is using a map and measuring the distance on the map.
so first you have to guess and then you will have to measure to see if you are right.